User blog comment:BurningWIKI/My Ditto and Phione won't breed!/@comment-31800919-20170707193250

A phione can breed with a ditto, if this is happening then its a bug its better to report it on the PBB discord.

"Breeding either Manaphy or Phione can produce a Phione Egg, but Phione is unable to evolve into Manaphy nor produce Eggs that can hatch into Manaphy. " from bulbapedia

https://bulbapedia.bulbagarden.net/wiki/Phione_(Pok%C3%A9mon)